Quick answer: 500 places, first come first served. Previous top-10 finishers may enter but cannot win again, and residents of the competition's restricted jurisdictions cannot take part.
The rules
Registration opens 3 days before each month begins; places are first come first served
Previous top-10 finishers may enter but are not eligible for a prize — this applies to any past Traderscale competition
Prize winners must take part in an interview with the team
Prizes are non-transferable and subject to compliance verification
Accessing the competition from a restricted jurisdiction results in immediate disqualification — see Competition Restricted Countries
See also: Monthly Competition Rules